Dental alloy and process of making the same



Patented Dec. 28, 1926.

UNITED STATES PATENT, OFFICE.

CLARENCE C. VOGT AND JOHN W. HARSCH, OF PITTSBURGH, PENNSYLVANIA, AS-

I SIGNORS TO LEE S. SMITH & SON MANUFACTURING COMPANY, OF PITTSBURGH,

PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

DENTAL ALLOY AND PROCESS OF MAKING THE SAME.

No Drawing.

The present invention relates to dental alloys, and more particularly to alloys for making the so-called amalgam or silver fillings.

The invention also relates to the process of making the improved alloy. The usual alloy for making amalgam or silver fillings consists principally of silver and tin, together with a small percentage of copper and zinc The alloy is furnished to the'dentist in finely divided condition, and is mixed with mercury and applied to the tooth cavity, where the amalgam sets or hardens. The setting action of the amalgam is usually believed to be due to a secondary reaction by which the mercury forms a metallic crystalline compound with the silver. The hardened filling apparently consists of crystals ofthisjmercury silver compound embedded in a matrix which consists principally of tin with possibly the copper and zinc.

The-usualdental alloys of the better class follow rather approximately the so-called Black formula, which in its specific form is silver67 parts, tin 27 parts, copper 5 parts I and zinc 1 part. Certain changes in these percentages are -made by different dental manufacturers in making alloys 1n accordance with the Black formula, the term' Black formula being used as a term of gpneral description of this class of dental a loys.

We have discovered that the dental alloys of the above class may be considerably strengthened, both as to resistance to crushing'and to shearing, by the addition to the alloy of nickel or cobalt. These two metals closely resemble each other physically and chemically. They are the two non-ferrous metals of the so-called iron or nickel group, which group consists of iron, nickel and cobalt. As far as .the action on the amalgam is concerned,.tliese'.two metals appear to be substantial equivalents.

In making up our improved alloy, we add a relatively small amount of nickel or cobalt, say up to about five er cent, referably about three per cent. ither nic el 'or cobalt maybe added alone, ora mixture of the two may be employed. The proportionof' the silver is reduced by about the amount of v added nickel or cobalt. A typical formula Application filed December 19, E23. SerialNo. 681,633.

which we have foundto be satisfactory is as follows: 1

-I'ans. Silver 63 Tin 28 Copper 5 Cobalt or nickel 3 Zinc 1- 'tin or tin and copper and add the silver to this alloy. The zinc is usually added just before pouring.

Since. the cobalt and nickel are insoluble in silver, but form' an alloy with tin, it is believed that the superior strength of the amalgam is due to increasing the strength of the tin matrix, the alloy of tin with cobalt or nickel being apparently stronger than tin without one of these alloying metals.

While we have described specifically the preferred proportions in our improved alloy for making amalgam fillings, and have described the preferred process of making such alloy, it is to be understood that the invention is not limited to the hereinbefore described details, but may be otherwise embodied within the scope of the following claims.

We claim:

1. A dental alloy containing silver and tin in amounts whichwill readily amalga mate with mercury to form a suitable hardening dental amalgam, together with a minor proportion of a non-ferrous metal of the nickel group.

2. A dental alloy containing majorproportiousof silver and tin anda minor proportion of a' nonaferrous metal of the nickel g p 3. A dental alloy made in approximate accordance with the Black formula but containing a small roportion of a non-ferrous metal of the nicfiel group.

4. A dental alloy made in approximate accordance with the Black formula but containing not overfive per cent of a non ferrous metal of the nickel group.

p 5. A dental alloy containing silver 50 to 70%, tin 25 to 40%, copper 3 to 7% and a non-ferrous metal of the nickel group 1 to 6. The process of making the herein described dental alloy comprising alloyingr a non-ferrous metal of the nickel group with 15 the tin and thereafter mixing the silver and till. I a

7 The process of making 'the herein described dental alloy comprising alloying a non-ferrous metal of the nickel group with 20 the'tin and copper and thereafter mixing the silver with the tin and copper;

In testimony whereof we have hereunto set our hands.

" CLARENCE C. VOGT.

JOHN W. HARSCH. 

